#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>

#define BUFFERSIZE	4096
#define COPYMODE 	0644

void oops(char *, char *);

int main(int ac, char *av[]){
	int in_fd, out_fd, n_chars;
	char buf[BUFFERSIZE];

	if (ac != 3){
		fprintf(stderr, "usage: %s source destination\n", *av);
		exit(1);
	}

	if ((in_fd = open(av[1], O_RDONLY)) == -1){
		oops("Cannot open ", av[1]);
	}
	if ((out_fd = creat(av[2], COPYMODE)) == -1){
		oops("Cannot creat ", av[2]);
	}
	while ((n_chars = read(in_fd, buf, BUFFERSIZE)) > 0){
		if (write(out_fd, buf, n_chars) != n_chars){
			oops("Write error to ", av[2]);
		}
	}
	if (n_chars == -1){
		oops("Read error from ", av[1]);
	}
	if (close(in_fd) == -1 || close(out_fd) == -1){
		oops("Error closing files", "");
	}
}

void oops(char * s1, char * s2){
	fprintf(stderr, "Error: %s", s1);
	perror(s2);
	exit(1);
}
